The cellular transcription factor HIF (Hypoxia Inducible Factor) occupies a central position in oxygen homeostasis in a wide range of organisms and is a key regulator of responses to hypoxia. The genes regulated by HIF transcriptional activity can play critical roles in angiogenesis, erythropoiesis, hemoglobin F production, energy metabolism, inflammation, vasomotor function, apoptosis and cellular proliferation. HIF can also play a role in cancer, in which it is commonly upregulated, and in the pathophysiological responses to ischemia and hypoxia.
The HIF transcriptional complex comprises an heterodimer: HIF is a constitutive nuclear protein that dimerizes with oxygen-regulated HIF subunits. Oxygen regulation occurs through hydroxylation of the HIF subunits, which are then rapidly destroyed by the proteasome. In oxygenated cells, the von Hippel-Lindau tumor suppressor protein (pVHL) binds to hydroxylated HIF-subunits, thereby promoting their ubiquitin dependent proteolysis. This process is suppressed under hypoxic conditions, stabilizing HIF and promoting transcriptional activation by the HIF complex.
Hydroxylation of HIF-subunits can occur on proline and asparagine residues and can be mediated by a family of 2-oxoglutarate dependent enzymes. This family includes the HIF prolyl hydroxylase isozymes (PHDs), which hydroxylate Pro 402 and Pro 564 of human HIF1, as well as Factor Inhibiting HIF (FIH), which hydroxylates Asn 803 of human HIF1. Inhibition of FIB or the PHDs leads to HIF stabilization and transcriptional activation. See, e.g., Schofield and Ratcliffe, Nature Rev. Mol. Cell Biol., Vo 15, pages 343-354 (2004).
Thus, new or improved agents that modulate (such as increasing HIF levels or activity) HIF are continually needed for developing new and more effective pharmaceuticals to treat HIF-associated conditions or diseases or disorders, such as ischemia, anemia, wound healing, auto-transplantation, allo-transplantation, xenotransplantation, systemic high blood pressure, thalassemia, diabetes, cancer, and an inflammatory disorder, to name a few. In discovering new or improved agents that modulate HIF level or activity, it is also desirable but not required to discover agents with improved chemical or biological properties such as solubility, bioavailability, pharmacokinetics, pharmacodynamics, toxicity and/or less side effects such as less cardiovascular side effects. The compounds, compositions, and methods described herein are directed toward these needs and other ends.